How to Collect and Use the Scum from Fermentation?

Collecting the Scum

The scum that forms on top of fermentation vessels, such as those used for making sauerkraut or kefir, is rich in beneficial bacteria and other microorganisms. To collect the scum, simply use a clean spatula to scrape it off the surface of the liquid, taking care not to disturb the underlying liquid. It’s best to collect the scum at regular intervals, ideally every few days, to ensure that it doesn’t become too thick and difficult to work with.

Using the Scum

The collected scum can be used to inoculate new fermentation vessels, adding beneficial microorganisms to the liquid and speeding up the fermentation process. In general, about 1-2% of the scum can be added to the new vessel, which can be enough to get the fermentation process started. For example, if you’re making a gallon of sauerkraut, you might add 1-2 tablespoons of scum to the brine before adding the shredded cabbage. The scum can also be used as a natural probiotic supplement, either on its own or as an ingredient in homemade fermented foods and drinks.